Epoxy resins are often used as adhesives, especially for adhering metal parts. Epoxy resins are typically one part of two-part adhesive compositions. The epoxy resin and a curing agent are typically mixed immediately prior to use, and cure within a certain amount of time. Many curing agents are nucleophilic compounds, such as amines or thiols, with at least two nucleophilic groups. Amine-based curing agents often have a relatively long cure time at low temperatures. Thiol (mercaptan)-based curing agents tend to react more rapidly, and at lower temperatures, than amine-based curing agents. Accordingly, thiol-based curing agents are preferred for certain applications.
U.S. Pat. No. 3,310,527 to De Acetis discloses certain thiol-based curing agents. These compounds include three or more -RSH groups attached to one or more aromatic rings, where R is alkyl, oxyalkyl or thioalkyl. However, De Acetis does not disclose or suggest how the oxyalkyl or thioalkyl groups would be incorporated onto the aromatic rings.
There is a need for curing agents for epoxy resins which can be easily prepared and which provide a relatively fast cure for epoxy resins. The present application provides such curing agents.